What knowledge should a programmer have in order to integrate a PHP script into ISPmanager?

Question

ISPmanager

Good afternoon.
Sorry for the stupid question, but I'm front-end and very weak in server-side programming. Essence of questions:
1) There is a PHP script and there is a server with ISPmanager, to be precise with (ISP Manager 5 Lite), my script needs to be integrated there as a module. What technology stack should a programmer have for such a task?
2) You need to change the appearance of ISPmanager, the design and layout will be. But what about the backend and template engine?
Thanks in advance